Probing the edge-related properties of atomically thin MoS2 at nanoscale

层状二维材料具有独特的物理化学性质，使其在光电器件、传感、能源和催化等领域得到了高度关注和广泛应用。二维材料在制备过程中不可避免引入结构缺陷，虽然这些缺陷尺度仅为数纳米甚至单原子，但是会极大地改变材料的结构和电子性质，从而影响其应用。化学化工学院任斌教授课题组在层状二维材料缺陷表征方面取得进展。该工作表明了TERS在原位、高空间分辨表征缺陷位的结构和电子性质方面具有独特的优势，可以进一步推广到其他二维材料，从而有效地指导缺陷设计和材料应用。 该工作通过校内外课题组紧密合作，在任斌教授、谭平恒研究员（中科院半导体研究所）和王翔博士共同指导下完成。实验部分主要由黄腾翔博士（第一作者，已毕业化学系博士生）完成，电子能带结构与光谱理论计算由谭平恒研究员课题组从鑫博士生（共同第一作者）完成，吴思思、林楷强、姚旭、何玉韩、吴江滨、包一凡、黄声超等参与了实验与讨论。【Abstract】Defects can induce drastic changes of the electronic properties of two-dimensional transition metal dichalcogenides and influence their applications. It is still a great challenge to characterize small defects and correlate their structures with properties. Here, we show that tipenhanced Raman spectroscopy (TERS) can obtain distinctly different Raman features of edge defects in atomically thin MoS2, which allows us to probe their unique electronic properties and identify defect types (e.g., armchair and zigzag edges) in ambient. We observed an edgeinduced Raman peak (396 cm−1) activated by the double resonance Raman scattering (DRRS) process and revealed electron–phonon interaction in edges. We further visualize the edge-induced band bending region by using this DRRS peak and electronic transition region using the electron density-sensitive Raman peak at 406 cm−1. The power of TERS demonstrated in MoS2 can also be extended to other 2D materials, which may guide the defect engineering for desired properties.The authors acknowledge the final supports from MOST of China (2016YFA0200601 and 2016YFA0301204), NSFC (21633005, 21790354, 21503181, 21711530704, 21621091, 11874350, 11474277, and 11434010), Natural Science Foundation of Fujian Province (2016J05046), and China Postdoctoral Science Foundation (2017M622062). 研究工作得到科技部、国家自然科学基金委员会、福建省自然科学基金和中国博士后基金资助

New observations for electron beam-induced instability of single-wall carbon nanotube

利用透射电镜在室温下对不同形态的单壁碳纳米管进行了原位电子束辐照研究.研究发现:在相同的辐照条件下随着辐照时间(或辐照剂量)的增加,两端固定的单壁碳纳米管径向收缩,且收缩速率越来越快;相同直径的轴向弯曲的单壁碳纳米管比平直的单壁碳纳米管更加不稳定;一端固定另端自由的单壁碳纳米管轴向收缩,但其直径基本不变.利用单壁碳纳米管纳米曲率效应和能量束诱导非热激活效应,对上述单壁碳纳米管的不稳定性现象进行了新的、合理的解释.The nanoinstability of single-wall carbon nanotube(SWCNT) under electron beam irradiation is systematically investigated by in-situ transmission electron microscopie observation at room temperature.Under the same irradiation condition,it is found that with the increase of irradiation time(or electron dose),the SWCNT whose two ends are fixed at ropes of nanotubes shrinks in its radial direction with an increasingly faster rate;the curved SWCNT is more instable than the straight one with the same diameter;the SWCNT with a free capped end but the other end fixed at a rope of nanotubes shrinks in the axial direction but almost keeps its diameter unchanged.All experimental phenomena could be well accounted for by new concepts of the nanocurvature of SWCNT and by the electron beam-induced athermal activation.国家科技计划国际科技合作与交流专项(批准号:2008DFA51230);国家重点基础研究发展计划(批准号:2007CB936603);国家自然科学基金(批准号:11074207;60776007);教育部高等学校博士学科点专项科研基金(批准号:20100121110023)资助的课题---

Effect of Organic Acid-Based Organosolv Fractionation of Eucalyptus on Pyrolysis Behavior of Its Derived Fractions

采用甲酸、乙酸及甲酸和乙酸的混合酸三种有机酸溶液对桉木进行预处理,考察有机酸预处理对其解构组分热解特性的影响。采用元素分析、红外光谱分析、热重–质谱联用等手段对预处理之后的固体残渣(富纤维组分)与未经处理桉木进行比较分析。采用热裂解器连接气质联用仪对预处理得到的富纤维素组分与木质素组分进行快速热裂解实验分析。实验结果表明：对桉木进行有机酸预处理,能有效地将纤维素、半纤维素、木质素分离,得到富纤维组分、高纯木质素和木糖。对富纤维素组分和木质素进行快速热解,左旋葡聚糖和苯酚类化合物的产率及选择性显著提高,其中乙酸与甲酸的混合酸预处理效果最好

松木预处理温度对生物油特性的影响

通过螺旋反应器低温预处理除去松木中的半纤维素和水分,然后用预处理得到的固体残渣来快速热解制生物油。固体残渣的化学组成分析和红外光谱分析表明,由于木质素含量的增加和炭化反应的发生,生物油的产率降低、焦和不可冷凝气的产率增加。随着预处理温度的升高,生物油水分含量减少,高位热值增加,运动黏度增加,密度增加,pH值先升高后降低,固体颗粒物含量增加。核磁共振碳谱分析表明,生物油的脂肪碳含量减少,芳香碳含量增加,芳香度增加

Measurement of integrated luminosity of data collected at 3.773 GeV by BESIII from 2021 to 2024

We present a measurement of the integrated luminosity e+e- of collision data collected by the BESIII detector at the BEPCII collider at a center-of-mass energy of Ecm = 3.773 GeV. The integrated luminosities of the datasets taken from December 2021 to June 2022, from November 2022 to June 2023, and from October 2023 to February 2024 were determined to be 4.995±0.019 fb-1, 8.157±0.031 fb-1, and 4.191±0.016 fb-1, respectively, by analyzing large angle Bhabha scattering events. The uncertainties are dominated by systematic effects, and the statistical uncertainties are negligible. Our results provide essential input for future analyses and precision measurements